# 1~10
# for i in range(1,11):
#     print(i)

#2,4,6,8,10
# for i in range(2,12,2):
#     print(i)

# 10~1
# for i in range(10,0,-1):
#     print(i)

thSum = 0
for i in range(1,101):
    thSum += i
print(thSum)